To find the numbers for which the rational expression is undefined, we need to find the values of x that make the denominator zero. In this case, the denominator is 5x-30. So, we set 5x-30 equal to zero and solve for x:
5x-30 = 0
5x = 30
x = 6
Therefore, the rational expression is undefined when x = 6.
In all other cases, when x is not equal to 6, the rational expression is defined for all real numbers.
Learn more about Finding undefined values in rational expressions